1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, more particularly, to an array substrate for an in-plane switching (IPS) mode LCD device being capable of displaying high quality images with an improved response rate.
2. Description of the Related Art
Generally, in the twist nematic (TN) mode LCD device, the pixel and common electrodes, by which a vertical electric field driving the liquid crystal (LC) layer is induced, are formed on different substrates.
On the other hand, in the IPS mode LCD device, the pixel and common electrodes are formed on the same substrate. A horizontal electric field is induced between the pixel and common electrodes, and the LC layer is driven by the horizontal electric field to have a wider viewing angle than the TN mode LCD device.
FIG. 1 is a schematic view showing an array substrate for an IPS mode LCD device according to the related art.
As shown in FIG. 1, display and non-display areas “DA” and “NA” are defined on a substrate 10. The non-display area “NA” surrounds the display area “DA”. Images are displayed in the display area “DA”. A plurality of data drivers 30 and a plurality of gate drivers 40 are formed on a plurality of tape carrier packages (TCPs) 20 in the non-display area “NA”. The data drivers 30 generate image signals to display images. The gate drivers 40 generate gate signals to control the data signals. The TCPs 20 and the display area “DA” are connected by a plurality of electric lines (not shown). The data drivers 30 are disposed on one side of the substrate 10, and the gate drivers 40 are disposed on another side of the substrate 10.
A plurality of data lines “Dm−1”, “Dm” and “Dm+1” and a plurality of gate lines “Gn” are formed in the display area “DA”. The data lines “Dm−1”, “Dm” and “Dm+1” and a plurality of gate lines “Gn” cross each other to define a plurality of pixel regions “P”. The data lines “Dm−1”, “Dm” and “Dm+1” are connected to the data drivers 30, and the gate lines “Gn” are connected to the gate drivers 40. Each pixel region P displays image having one of red “R”, green “G” and blue “B” colors.
A common electrode “CE” and a pixel electrode “PE” are formed in each pixel region “P” on the substrate 10. A horizontal electric field is induced between the common and pixel electrodes “CE” and “PE”. The common and pixel electrodes “CE” and “PE” may have an angle less than about 45 degrees with respect to the data lines “Dm−1”, “Dm” and “Dm+1”. The common and pixel electrodes “CE” and “PE” may be parallel to the data lines “Dm−1”, “Dm” and “Dm+1” and alternately arranged with each other. The LCD layer is formed over the common and pixel electrodes “CE” and “PE”. A rubbing process is performed to the LCD layer according to an arrow as shown in FIG. 1 to display black images when voltages are applied to the common and pixel electrodes “CE” and “PE”. It may be referred to as a normally black mode.
FIGS. 2A and 2B are a perspective view for explaining arrangements of LC molecules of an IPS mode LCD device according to the related art.
As shown in FIG. 2A, when voltages are not applied to the pixel and common electrodes “PE” and “CE”, the LC molecules “LC” are aligned along an initial alignment direction.
As shown in FIG. 2B, when voltages, for example, 7 and 0 voltages are respectively applied to the pixel and common electrodes “PE” and “CE”, are applied to the pixel and common electrodes “PE” and “CE” and the horizontal electric field are generated between the common and pixel electrodes “CE” and “PE”, the LC molecules “LC” are aligned along a direction of the horizontal electric field. The LC molecules “LC” have different light transmittances depending on magnitude of the electric field. It may be called a rising step.
When the electric field between the common and pixel electrodes “CE” and “PE” are removed after the rising step, the LC molecules “LC” are realigned to the initial alignment direction. It may be called a falling step.
Movements of the LC molecules, such as the rising step and the falling step, appear in not only the IPS mode LCD device but also other display devices.
In the rising step, the LC molecules “LC” are responsive to the electric field such that they are quickly aligned along the direction of the electric field. However, in the falling step, the LC molecules “LC” are less responsive than the rising step. It is because the LC molecules “LC” are realigned to the initial alignment direction depending on the characteristics of the LC molecules and an alignment layer, for example, an elastic coefficient, a rotational viscosity, an aligning force, and so on.
Since the LC molecules “LC” are slowly realigned in the falling step, the LC molecules “LC” have undesired alignment in the next frame and the LCD device can not display desired images.